1. Field of the Invention
The invention relates to a clamp assembly for releasable securing a flexible material within the clamp assembly and the use of this clamp assembly to tension or support the flexible material and is particularly useful in the tensioning of flexible material signs, awnings, screens, etc.
2. Description of the Prior Art
This invention is an improvement to the tensioning assembly utilized in Coleman U.S. Pat. No. 5,398,388 to make a sign facing formed of flexible material tight against a sign frame.
It is known in this art to provide a means for securing the edges of flexible material, be it a sign, an awning, a screen, a silkscreen etc., to some form of clip or clamp and then to use the clips with a frame structure to tension the flexible material across the frame. All these clips are provided with some form of cavity that is designed to receive the edge of the flexible material and retain the material therein. In U.S. Pat. No. 2,335,361, the flexible material is physically crimped in the clip channel. Although the material is secured, such physical deformation clearly could damage the flexible material. A number of other patents wrap the flexible material about a bar and use tabs in the clip cavity or use the edges of the clip cavities to secure the wrapped bar within the cavity (see U.S. Pat. No. 4,955,928, U.S. Pat. No. 5,033,216, U.S. Pat. No. 5,398,388 and U.S. Pat. No. 5,467,546). The wrapped bar in each of these instances was secured in the cavity only at the points where the tabs or cavity edges engaged the wrapped bars. In U.S. Pat. No. 4,955,928 the wrapped bar was secured by small outer legs 54 and 42 at the cavity opening. In U.S. Pat. No. 5,033,216 the wrapped bar was secured by prongs 60 and 70 at the rear of the clip. In U.S. Pat. No. 5,398,388 the wrapped bar was secured by leg 36 at the cavity opening. In U.S. Pat. No. 5,467,546 the edge of the flexible material was wrapped about a U-shaped spline, which defined a trough, and the wrapped spline was inserted into the clip cavity which contained detents which snapped into the trough thereby deforming the fabric in the trough. In this manner the fabric margin was grasped or secured in the clip cavity by the detents interaction with the trough. Although the flexible material was secured in the cavity in all these patents, the only physical grip on the flexible material was at very small points or areas on the cavity wall where the wrapped bar was engaged when tensioned. In U.S. Pat. No. 5,467,546, for example, which secured the wrapped bar in the cavity by detents, when the fabric was tensioned, the fabric pulled the wrapped spline to pinch it at a pinch point 24 on only one side of the clip cavity. This means for securing as well as the other prior art, which secure at only small points or areas are substantially different from applicant's means for securing, which secures and locks the flexible material simultaneously to approximately 90% of the cavity's surface. Although the above prior art means for securing grip the fabric in the cavity, they do it in an entirely different manner with an entirely different result.
There are still other patents that describe wrapping the flexible material about a bar and placing the wrapped bar in a clip or clamp cavity. The bars utilized in these patents are in the form of circular, square or elongated bars that are placed in cavities that are complimentary in shape to the bars so that when the fabric is tensioned a larger surface area of the fabric is clamped in the cavity (see U.S. Pat. No. 3,485,165, U.S. Pat. No. 4,265,039, U.S. Pat. No. 4,409,749. U.S. Pat. No. 4,554,754, U.S. Pat. No. 5,042,182, U.S. Pat. No. 5,301,447 and U.S. Pat. No. 6,339,889). Although these references appear to provide a stronger grip on the fabric than the previous references, the grip was only either a portion of an arc of a circle, one side of a square or two sides of a four side element. In U.S. Pat. No. 4,409,749 a wrapped four sided bar with two tapered sides was placed in a tapered channel. When the fabric was tensioned it was gripped in the channel by the tapered sides of the bar. In U.S. Pat. Nos. 3,485,165, 4,265,039, 4,554,754, 5,042,182, 5,301,447 and 6,339,889 wrapped circular bars were placed in circular channels. When the fabric was tensioned, it was gripped at a small arc of the channel. Reference U.S. Pat. No. 6,339,889 also taught a wrapped rectangular bar placed in a rectangular channel. When the fabric was tensioned, it was gripped at only one side of the rectangular channel.
None of the above cited references teaches wrapping the flexible material about a triangular bar with two major surfaces joined at the apex by an acute angle and whose major surface lengths are at least three times the height of its base and the insertion of the wrapped bar into a clamp channel that has a base and two sloping side walls that are congruent to the sides of the triangular bar within the channel. This latter structure provides an almost 90% gripping surface area for the flexible material, which far exceeds the gripping surface area of the prior art. An even larger gripping surface area could be obtained by further reducing the acute angle of the triangular bar.
In many of the prior art tensioning devices noted above, the entire securing means of the fabric takes place within the clip itself. If the clip fails for whatever reason, and they are known to do so, it could result in slippage of the material from the cavity, severe stress to the material resulting in deformation of the material, and in some instances tearing of the material. Since many of these prior art clips are made from flexible material, particularly in the area where they secure the fabric, when this part of the clip fails, so does its grip on the fabric. For example in U.S. Pat. No. 2,335,361 the fabric margin is secured to the clip by crimping the fabric between two flexible legs. Should either leg break, the fabric will pull free. Similarly in U.S. Pat. No. 5,467,546, the fabric margin is secured to the clip by flexible legs having detents that grasp the fabric margin to the clip. If either of these legs fail, the uniform grip on the fabric is lost and the stress in the fabric will cause slippage of the fabric or, at the very least, distortion of the fabric being tensioned. In U.S. Pat. No. 5,033,216 the fabric retaining clip is made of flexible sheet metal with the fabric margin being retained in the clip by very small prongs. Should this clip fail or just the small prongs of the clip fail, the fabric would slip or deform and the uniform tensioning would be lost.
The present invention's clamping means eliminates all these problems by not only providing a more secure means of internal clip flexible material retention but also additionally providing an external clamping of the flexible material. Applicant's solution to this problem consists of two features. First, the clip or clamp that grasps the marginal edge of the fabric internally of the clip is made of a rigid nonflexible material. Because of this rigidity, it is highly unlikely that the clip itself will fail and loose its grip on the fabric. Additionally applicant's unique triangular internal clamping design provides maximum surface area gripping force on the flexible material. Secondly, in addition to the securely clamping the fabric margin internally of the clip, the fabric margin is extended out of the clip and is additionally externally clamped to the clip receiving channel wall as a result of pivotal movement of the tensioning clip as the fabric is tensioned. In a first embodiment, the fabric margin is wrapped about a triangular bar and secured within the clip with the fabric margin extending out of the clip. As the fabric margin extends from the interior of the clip, it overlaps the main body of the fabric and this double layer of fabric is then clamped between an external edge of the clip and the receiving channel wall when the clip pivots as a result of the fabric tension. In a second embodiment, the fabric margin is wrapped about a triangular bar and secured within the clip with the apex of the wrapped bar extending externally of the clip. Again, as in the first embodiment, as the fabric margin extends from the interior of the clip, it overlaps the main body of the fabric and this double layer of fabric is clamped between an external edge of the clip and the receiving channel wall when the clip pivots as a result of the fabric tension. In one version of this embodiment, however, the apex of the wrapped triangular bar additionally clamps a single layer of the fabric to the receiving channel wall in addition to the double layer clamping when the clip pivots as a result of the fabric tension.
In alternate versions of the above mentioned embodiments, the fabric margin is wrapped about the triangular bar and overlapped upon itself with its free end secured within the clip so that only a single layer of the fabric extends from the interior of the clip. In this alternative to the first embodiment, the single layer is clamped between the external edge of the clip and the receiving channel wall when the clip pivots as a result of the fabric tension. In this alternative to the second embodiment, when the free end of the fabric margin is secured within the clip and a single layer of the fabric extends from the clip, the single layer is clamped between the external edge of the clip and the channel wall. In this embodiment, however, a double layer of fabric is clamped between the apex of the triangular bar and the channel wall upon clip rotation.
The only prior art fabric tensioners that formed any type of external clamping in addition to internally securing the fabric margin within the clip were U.S. Pat. No. 5,255,459 and applicant's own Patent U.S. Pat. No. 5,398,388. In U.S. Pat. No. 5,255,459, only a single layer of fabric is clamped between an external edge of the clip and the receiving channel wall, not the overlapped double layer clamping taught by applicant. Furthermore, this reference fails to teach the unique additional external clamping or locking of the fabric margin between the external portion of the clamp as well as the clamping or locking by the apex of the triangular bar. In addition, this reference also differs from applicant in that it secures a single layer of the fabric within the clip by physically puncturing the fabric to retain it within the clip. There is no internal channel or recess within the clip that interacts in any way with a bar or spline wrapped with the fabric. Although applicant's above noted patent performs a double layer external clamping, it does not employ the novel and efficient internal clip clamping achieved by the triangular shaped bar of all the embodiments of the present invention nor does it teach the additional external clamping between the triangular bar apex and the receiving channel wall of one of the embodiments.